The objective of the proposed research is to find a new index of ventricular contractility which is clear in concept, relatively simple to measure and more sensitive to the changes in the state of the heart. Based on previous work, we propose that the time-varying pressure/volume ratio (e(t) ) of a contracting ventricle serves as a good index of cardiac contractility. Our experimental analysis indicate that the above ratio, calculated after a slight correction of volume, is reasonably independent of pre- and afterload, and yet varies markedly with changes in the inotropic background. Our theoretical analysis showed that the ratio is very closely related to the parameters of force-velocity curve (Vmax and Po). In the first year, we reconfirmed our previous experiments as thoroughly as possible, using a cardiometer for left ventricular volume measurement and a miniature transducer for ventricular pressure in a denervated heart. e(t) was confirmed to be independent of mechanical loading and the effects of various inotropic interventions on it was quantified in terms of changes in the maximum e(t) and theand the time to this peak e(t). In the second year, we modified the volume measurement using simultaneously an ultrasound technique with implanted crystal transducers and a new volumetric system in excised dog hearts. The data of the study serve as reference for the accuracy of e(t) measured by indirect volume estimations from echocardiograph. In the third year, the index will be measured and tested in patients using echocardiography and/or cinecardiography and evaluate the clinical utility of the e(t) index in comparison with other indices of cardiac contractility. We will also investigate the feasibility of using the end-diastolic P/V ratio value as a simplification of e(t) for clinical use.